I fitted experimental data to obtain the best suited isotherm using Rstudio and CAVS. Redlich-peterson model was the best fit. However, the softwares generated a beta value above 1(1.99 and 2.44 respectively)
I gleaned from literature review that beta value can only be between 0 and 1. Please how do I discuss my beta value with relations to type of adsorption (Physisorption or chemisorption) in my system
PS: Origin software gave a value of 0.88, why the disparity between softwares ?
Dear Amen Ekhosuehi.
Even although the literature suggest that the beta parameter of the R-P adsorption isotherm model moves between 0 - 1, it is known that this value can get over this range. Please consider this text: https://doi.org/10.1016/j.cej.2010.03.006
The exact explanation depends on your specific system. Nevertheless, I would suggest you to supervise the fitting procedures because the desviation between the two experimental values for a unique isotherm is too high.
If you need help to fit the model, please let me know and I will help you.
Amen Ekhosuehi, The R-P isotherm is an empirical one. Therefore, I would not attach great importance to the value of the parameters obtained as a result of fitting this function to the equilibrium data. These are some numbers that have no physical meaning. Let me add that the exponent in the denominator greater than 1 implies a maximum on the equilibrium curve. This is obviously impossible for pure adsorption. You also noticed differences in parameter values when using different software. It is possible and the reasons may be different measures of fit, stop criteria, or different methods of selecting the starting point. But this is just a guess, because one would have to get familiar with the source code of the software and the numerical methods used.
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